Cracking over contaminated catalyst

ABSTRACT

A process for cracking, in the absence of hydrogen, a gas oil charge, which comprises contacting said gas oil charge under catalytic cracking conditions with a catalyst, consisting of a crystalline aluminosilicate, having an exchangeable sodium content of less than 4 weight percent, contained in a porous matrix, which catalyst has impregnated thereon, prior to contact with said gas oil charge, a controlled amount of nickel, iron or vanadium in an amount of 100 to 1,000 ppm. of at least one of said metals and recovering from the cracked products, a gasoline of higher octane number than that capable of realization by cracking said charge under identical conditions with an otherwise identical catalyst, but which had not undergone initial impregnation with at least one of said metals.

United States Patent [191 Stover Feb. 27, 1973 [75] Inventor: William A.Stover, Woodbury, NJ. [73] Assignee: Mobil Oil Corporation, New York,

[22] Filed: Dec. 28, 1970 [21] Appl. No.: 102,128

[52] US. Cl ..208/120 [51] Int. Cl. ..C10g 11/02, ClOg 11/04 [58] Fieldof Search ..208/120 [56] References Cited UNITED STATES PATENTS3,509,042 4/1970 Miale ..208/l20 3,271,418 9/1966 Plank et al.....208/l20 3,210,267 10/1965 Plank et al.... .....208/120 3,276,99310/1966 Reid .....208/l20 3,143,491 8/1964 Bergstrom .....208/120 X2,914,459 ll/1959 Mills et al. .....208/l20 X 3,400,072 9/1968 Tung eta1. .....208/120 3,150,075 9/1964 Russell et al. ..208/120 3,255,1026/1966 Sanford et al. .....208/l20 3,146,188 8/1964 Gossett ..208/l20 X3,120,484 2/1964 Mills et al ..208/l20 Primary Examiner-Patrick P.Garvin Assistant Examiner-P. F. Shaver Attorney-Oswald G. Hayes, AndrewL. Gaboriault, Raymond W. Barclay and James F. Woods [57] ABSTRACT Aprocess for cracking, in the absence of hydrogen, a gas oil charge,which comprises contacting said gas oil charge under catalytic crackingconditions with V a catalyst, consisting of a crystallinealuminosilicate, having an exchangeable sodium content of less than 4weight percent, contained in a porous matrix, which catalyst hasimpregnated thereon, prior to contact with said gas oil charge, acontrolled amount of nickel,

iron or vanadium in an amount of 100 to 1,000 ppm. of at least one ofsaid metals and recovering from the cracked products, a gasoline ofhigher octane number than that capable of realization by cracking saidcharge under identical conditions with an otherwise identical catalyst,but which had not undergone initial impregnation with at least one ofsaid metals.

12 Claims, No Drawings CRACKING OVER CONTAMINATED CATALYST BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention is directed tothe cracking of gas oils with a catalyst which contains a controlledamount of a contaminant metal such as iron, nickel or vanadiummaintained on a crystalline aluminosilicate zeolite.

2. Discussion of the Prior Art The cracking of gas oils over crystallinealuminosilicate zeolites is broadly known and disclosed in numerouspatents such as US. Pat. No. 3,140,249. Crystalline aluminosilicatezeolites, especially in a rare earth metal form contained in a matrix ofsilica or silica-alumina, provide superactivity and excellent yields ofhigh octane products at standard cracking conditions. Certain metalssuch as nickel, iron and vanadium have heretofore been known to becontaminants in the cracking of gas oil charge stocks. These metals arenor mally considered to be catalyst poisons in cracking operationscarried out in the absence of hydrogen. However, it has now been foundthat these metals can indeed be useful components of a catalystcomprising a crystalline aluminosilicate zeolite for normal catalyticcracking to provide products of a still higher octane number thanobtained from a similar operation, but in which the catalyst does nothave the above specified metals initially impregnated thereon.

SUMMARY OF THE INVENTION A process for cracking, in the absence ofhydrogen, a gas oil charge which comprises contacting said gas oilcharge under catalytic cracking conditions with a catalyst consisting ofa crystalline aluminosilicate, having an exchangeable sodium content ofless than 4 weight percent, contained in a porous matrix, which catalysthas impregnated thereon, prior to contact with said gas oil charge, acontrolled amount of nickel, iron or vanadium in an amount of 100 to1,000 ppm. of at least one of said metals and recovering from thecracked products, a gasoline of higher octane number than that capableof realization by cracking said charge under identical conditions withan otherwise identical catalyst, but which had not undergone initialimpregnation with at least one of said metals.

DESCRIPTION OF PREFERRED EMBODIMENTS The essence of the presentinvention involves the utilization of materials heretofore consideredcracking catalyst poisons when contained in gas oil feed stocks. Thesemetals, iron, nickel and vanadium, when present in minor quantities ingas oil have been found to have a deleterious effect upon crackingcarried out in the absence of a hydrogen atmosphere. The discovery thatby employing a pre-impregnated catalyst containing a controlled amountof nickel, iron or vanadium in an amount of 100 to 1,000 ppm. based onmoisture-free the combined metal contaminant content of the gas oilfeed. The catalyst should initially contain between and 1,000 ppm. of atleast one of said metal contaminants based on the weight of the finishedcatalyst. However the upper limit could be considered extremelyimportant in that should the gas oil contain a high amount of metalcontaminants such as above 5 ppm., the catalyst could becomecontaminated to such an extent that the desirable yield of crackedproducts such as gasoline at the expense of coke will not be obtained.Of course, if the gas oil feed is free of metal contaminants, theprocess can be conducted with a catalyst at the upper metal contaminantcontent level of 1,000 ppm.

Cracking catalysts pursuant to the present invention comprise acrystalline aluminosilicate zeolite component and an amorphous matrixmaterial which-itself may be active or inactive. Crystallinealuminosilicate zeolites contemplated are those known as molecularsieves and are characterized by high catalytic activity. Such zeolitescan be either natural or synthetic. Particularly contemplated naturalzeolites include faujasite, chabazite, and mordenite as well as thesmaller pore zeolites such as offretite and erionite. Synthetic zeolitesparticularly contemplated include especially zeolites X, Y, A, T, alpha,beta, ZK-4, ZK-S, ZSM-4, as described in British Pat. No. 1,117,568 andZSM5 as described in Belgian Pat. No. 713,516. It is to beunderstood,that other natural and synthetic zeolites are alsocontemplated as the zeolite component of the catalyst of the presentinvention. The crystalline aluminosilicate zeolite component of thecatalyst is in a low alkali metal form, i.e., contains less than 4weight percent alkali metal, usually sodium. Preferably, the alkalimetal content is below 1 weight percent. Reduction of the alkali metalcontent is accomplished by exchange with a source of hydrogen cations orcations decomposable to hydrogen or a desired metal cation especiallymetals of Groups II-VIII of the Periodic Table. Of these metals, it ispreferred that a rare earth metal or mixture of rare earth metals be thedesired metal cation of the crystalline aluminosilicate. Additionally,the controlled amount of iron or nickel can be placed on the catalyst byion exchange in which case the ion exchange technique accomplishes adual function-reduction of the alkali metal content and the depositionof the desired controlled amount of iron or nickel.

Ion exchange is accomplished in the known manner by using a salt of thedesired metal in a solution, usually an aqeuous solution. Thetemperature of the ion exchange solution is usually at room temperaturealthough good results are obtained employing a solution having atemperature up to the boiling point of the solvent. Under pressureconditions, the temperatures higher than the normal boiling point of thesolution can be employed. The ion exchange can be performed on thezeolite component before or after admixture with the porous matrixmaterial. Excellent results are achieved by ion exchanging thecrystalline aluminosilicate apart from the matrix material and calciningthe so exchanged material at a temperature of 500-l,500 F. prior toincorporation of the zeolite component with the matrix. The matrix isthereafter exchanged when in admixture with the zeolite component whichexchange effectuates still further reduction of the alkali metalcontent. It should be noted that one can, for instance, ion exchange thecrystalline aluminosilicate zeolite with a rare earth salt solution,calcine it, incorporate the aluminosilicate with the porous matrixmaterial and accomplish further exchange of the combined materials withthe controlled amounts of nickel and iron in which case alkali metals inboth components will be removed and the controlled amounts of addedmetals will be deposited uniformly throughout the catalyst composition.

The crystalline aluminosilicate component either before or afterexchange with the desired metal, e.g., rare earth incorporation thereinof the controlled amounts of iron, nickel or vanadium is intimatelycombined with a porous amorphous matrix material. Such materials includeactive and inactive materials and synthetic or naturally occurringzeolites as well as inorganic materials such as clays, silica and/ormetal oxides. The latter may be either naturally occurring or in theform of gelatinous precipitates or gels including mixtures of silica andmetal oxides. Use of a material in conjunction with the zeolite, i.e.,combined therewith which is active, tends to improve the conversionand/or selectivity of the catalyst in certain organic conversionprocesses. Inactive materials suitably serve as diluents to control theamount of conversion in a given process so that products can be obtainedeconomically and orderly without employing other means for controllingthe rate of reaction. Normally, non-fluid zeolite catalyst materialshave been incorporated into naturally-occuring clays, e.g., bentoniteand kaolin, to improve the crush strength of the catalyst undercommercial operating conditions. These materials, i.e., clays, oxides,etc., function as binders for the catalyst. It is desirable to provide acatalyst having good crush strength because in a petroleum refinery thecatalyst is often subjected to rough handling, which tends to break thecatalyst down into powder-like materials which cause problems inprocessing. These clay binders have been employed normally only for thepurpose of improving the crush strength of the catalyst.

Naturally occurring clays which can be composited with the zeolitecomponent include the montmorillonite and kaolin family, which familiesinclude the sub-bentonites, and the kaolins commonly known as DixieMcNamee-Georgia and Florida clays or others in which the main mineralconstituent is halloysite, kaolinite, dickite, nacrite, or anauxite.Such clays can be used in the raw state as originally mined or initiallysubjected to calcination, acid treatment or chemical modification.Binders useful for compositing with the zeolite component also includeinorganic oxides, notably alumina.

In addition to the foregoing materials, the zeolite can be compositedwith a porous matrix material such as silica-alumina, silica-magnesia,silica-zirconia, silicathoria, silica-beryllia, silica-titania as wellas ternary compositions such as silica-alumina-thoria,silica-alumina-zirconia, silica-alumina-magnesia andsilica-magnesia-zirconia. The matrix can be in the form of a cogel. Therelative proportions of finely-divided crystalline aluminosilicate, andinorganic oxide gel matrix vary widely with the crystallinealuminosilicate content ranging from about 1 to about 90 percent byweight and more usually, particularly when the composite is prepared inthe form of beads, in the range of about 2 to about 50 percent by weightof the composite. The matrix material may also have clay incorporated,usually added with the component to be cogelled.

Employing the catalyst of this invention for catalytic cracking,hydrocarbon cracking stocks can be cracked at a liquid hourly spacevelocity between about 0.5 and 50, a temperature between about 550F. and1,l00F., a pressure between about subatmospheric and several hundredatmospheres.

In order to more fully illustrate the nature of the present inventionand the manner of practicing the same, the following examples arepresented:

EXAMPLE 1 12,120 Grams of Q-Brand sodium silicate were dissolved inpounds of water and mixed well. The solution was heated to 120F. To theheated solution was added 340 cubic centimeters of 96.8 percent H 80, toa final pH of 10.1. The solution was heated to F. and held at 140F. for3 hours during which the silicate formed a gelled slurry. To the gelledslurry was added 20 percent Al (SO solution containing 3,024 grams Al(SO 14 B 0 at a uniform rate over a A hour period. The amount ofaluminum sulfate was sufficient to give about 13 percent alumina basedon the weight of the silica-alumina matrix being formed. The resultantpH was 3.5. Thereafter, a saturated solution of sodium carbonate wasadded until the pH measured 4.7.

A sample of zeolite Y which had been initially exchanged with rare earthchloride solution to a sodium content of about 3 percent by weight andthen calcined, was dispersed in a rare earth chloride solution.Specifically, 216 grams of the calcined REY were dispersed in a solutionof 64 grams RECI 6 H O in 600 cubic centimeters water. The dispersed REYin the solution was added to the 4.7 pH silica-alumina gelled slurry,and the resultant material was homogenized and spray dried. The driedproduct was twice slurried with 6 gallons of water, let settle and thesupernatant liquid was decanted. It was placed in a column andcontinuously exchanged by passing 20 gallons of an aqueous 5 percentammonium sulfate solution through the columns. Thereafter, it was waterwashed until the effluent was substantially free of sulfate ion. It wasthen dried at 250F. The resultant material was mixed with a short-residcontaining metals in an amount equal in weight to the compositecatalyst. The so impregnated material was burned clean of the bumableportion of the short resid by heating it to l,l0OF. in air, depositingthe metals onto the catalyst. Thereafter, the metal impregnated catalystwas steamed for 4 hours at l,400F. at atmospheric pressure.

EXAMPLE 2 Two pounds of a commercially available 13X zeolite weresubjected to two 3 hour ion exchanges each with 3 liters of 0.333 molarlanthanum chloride aqueous solution. The exchange was performed at roomtemperature. The resultant material was calcined for 5 hours at 900F. inair. Thereafter, it was exchanged once for 20 hours with 3 liters of a 1molar nickel chloride solution at room temperature. It was againcalcined for 5 hours at 900F. in air and analyzed. The analysis of theproduct is set forth below.

COMPOSITION OF PRODUCT COMPONENT PERCENT, WT. Sodium 0.75

Silica 41.9

Rare Earth Oxide 23.7

Alumina 28.5

Nickel 3.08

7,575 grams of Q-Brand sodium silicate were dissolved in 100 pounds ofwater and mixed well. The solution was heated to 120F. and 96.1 percentsulfuric acid was added at a uniform rate of 1% hour period. A total of212 cubic centimeters were added. The resultant pH of the solution was10.2.

The solution was heated to 140F. and held at 140F. for 2 hours duringwhich the silicate formed a gelled slurry. To the gelled slurry wasmixed in 20 percent AL2(SO4)3 solution containing 1,890 grams Al2(SO4)314 11,0 so that the resultant silica-alumina matrix material willcontain about 13 percent by weight alumina-The pH at this stage wasdetermined to be 3.6. A saturated solution of sodium carbonate was addedthereto to adjust the pH to 4.5 and 5.0. After 800 cubic centimeters ofthe solution was added, the pH was determined to be 4.8.

209 grams of the rare earth nickel zeolite X prepared in accordance withthe first stated paragraph above was dispersed in a solution of 63 gramsof RECl 6 H O (where RE means rare earth) in 600 cubic centimeters waterto 7.5 weight percent RENiX. The RENiX dispersed in RECl 6H,O solutionwas mixed into the silica-alumina slurry. The dispersion was homogenizedand spray dried. The dried product was slurried with 6 gallons of waterand then allowed to settle. The water was decanted. This was performedtwice. The product was placed in a column and then exchangedcontinuously with 15 gallons of an aqueous 5 percent (NH4 S04 solution.Thereafter, it was washed sulfate free and dried at 275-300F. Thematerial was steamed for 4 hours at 1400F. under atmospheric pressure.

EXAMPLE 3 The catalysts of Examples 1 and 2 were evaluated for fluidcatalytic cracking of a wide cut Mid Continent gas oil. Both catalystmaterials had particle sizes between and 150 microns in diameter. Theywere evaluated against the same catalyst which did not contain addedmetals. The cracking was performed at 925F. at a 5 weight hourly spacevelocity. The weight ratio of catalyst to oil was 5. In Table 1 below,there is set forth the comparative data of the two materials against thecontrol catalysts.

TABLE 1 Effect of Metals Activation on Product A Quality from ZeoliticFluid Catalyst Ex. 1 Ex. l Ex. 2 Ex. 2 Con Con trol trol metals Added,ppm. Ni 80 0 180 0 V 92 0 0 0 Fe 480 0 0 0 Cu 10 0 0 0 From the abovetable, it can be seen that in both instances, the catalyst having aminor amount of added metal provides significantly better results interms of the octane value of the gasoline fraction. It is seen from thisdata that this difference is a significant one which is independent ofthe method by which the metals are added to the cracking catalyst or thenature of the specific molecular sieve catalyst employed. These resultsare considered particularly surprising since added metals have long beenregarded as poisons. That such materials provide beneficial results isnot predictible from the state of the art.

I claim:

1. A process for cracking, in the absence of hydrogen, a gas oil charge,characterized by a combined metal contaminant content of iron, nickeland vanadium of less than 5 ppm. which comprises contacting said gas oilcharge under catalytic cracking'conditions with a catalyst consisting ofa crystalline aluminosilicate zeolite, having an exchangeable sodiumcontent of less than 4 weight percent, contained in a porous matrix,which zeolite is in a rare earth exchanged form and said matrix hasimpregnated thereon, prior to contact with said gas oil charge, acontrolled amount of nickel, iron, vanadium or combinations thereof inan amount of to 1,000 ppm. of at least one of said metals, andrecovering from the cracked products a gasoline of higher octane numberthan that capable of realization by cracking said charge under identicalconditions with an otherwise identical zeolite catalyst and matrix butwhich had not undergone impregnation on the matrix with at least one ofsaid metals prior to contact with said gas oil charge.

2. A process according to claim 1 wherein the crystallinealuminosilicate is zeolite X.

3. A process according to claim 2 wherein said zeolite X is compositedwith an inorganic oxide matrix material.

4. A process according to claim 3 wherein said inorganic oxide matrixmaterial is silica-alumina.

5. A process according to claim 1 wherein said crystallinealuminosilicate is zeolite Y.

6. A process according to claim 5 wherein the rare earth exchangedzeolite Y is composited with an inorganic oxide matrix material.

7. A process according to claim 6 wherein said inorganic oxide matrixmaterial is silica-alumina.

8. A process according to claiin 1 wherein said matrix contains nickel.

9. A process according to claim 1 wherein said matrix contains acombination of nickel, iron and vanadium.

10. A process according to claim 4 wherein the zeolite contains hydrogenions.

11. A process according to claim 7 wherein the zeolite contains hydrogenions.

12. A process according to claim 1 wherein the zeolite has a particlesize between 10 and microns.

2. A process according to claim 1 wherein the crystallinealuminosilicate is zeolite X.
 3. A process according to claim 2 whereinsaid zeolite X is composited with an inorganic oxide matrix material. 4.A process according to claim 3 wherein said inorganic oxide matrixmaterial is silica-alumina.
 5. A process according to claim 1 whereinsaid crystalline aluminosilicate is zeolite Y.
 6. A process according toclaim 5 wherein the rare earth exchanged zeolite Y is composited with aninorganic oxide matrix material.
 7. A process according to claim 6wherein said inorganic oxide matrix material is silica-alumina.
 8. Aprocess according to claim 1 wherein said matrix contains nickel.
 9. Aprocess according to claim 1 wherein said matrix contains a combinationof nickel, iron and vanadium.
 10. A process according to claim 4 whereinthe zeolite contains hydrogen ions.
 11. A process according to claim 7wherein the zeolite contains hydrogen ions.
 12. A process according toclaim 1 wherein the zeolite has a particle size between 10 and 150microns.